Some of the most challenging tasks for current Traction Control (TC) systems include situations where a vehicle is “stuck” in (deep) snow or mud, or on a possibly icy and/or inclined road.
One approach to vehicle traction control in non-moving conditions is described in U.S. Pat. No. 5,265,693. In this example, higher slip may be used if controller senses a non-moving (stuck) vehicle. In another approach (U.S. Pat. No. 5,735,362), the controller uses a combination of a controlled increase in target wheel slip and subsequent phases that reduces driving power and torque to the wheels.
However, the inventors herein have recognized potential issues with such approaches. For example, the use of solely higher slip may actually cause the vehicle to become more entrenched and reduce the ability of the operator to move the vehicle. Also, in continuing traction control intervention that still may not move the vehicle, the operator may become frustrated to the point of turning the traction control system off, and trying to negotiate the situation without traction control active. These issues may lead to decreased customer satisfaction.
In one approach, a system is used, including a traction control system configured to adjust powertrain output to reduce wheel slip; and a powertrain controller configured to control powertrain output based on actuation of a pedal of the vehicle by the driver, where a relationship between powertrain output and pedal actuation is adjusted in response to at least one of road grade and direction of wheel spin.
In one example, road grade can be used in adjusting the powertrain output and the relation between the pedal and engine/powertrain output to provide better control when overriding the driver request. In another example, the direction of wheel travel can be used.
In one example, if overriding driver actuation to perform traction control still results in a non-moving vehicle condition, for example, the traction management system can return control to the driver, but with finer resolution at lower torques to better navigate the condition. Further, the duration of the altered driver resolution can be extended or shorted depending on various conditions. Fore example, the vehicle's powertrain response behavior to a command input may be modified if a non-moving condition is identified in order to provide the driver higher resolution powertrain torque output control for longer periods if going up an incline. In this way, improved vehicle performance may be achieved, and improved customer satisfaction obtained.
In another example, the vehicle's powertrain response behavior can be returned to that which corresponds to a moving vehicle at various times depending on a gear position, or based on a driver actuated switch identifying road conditions. This transition may be gradual, in one example, so that driver perception of the transition may be reduced.
Note that various types of relations may be used, such as linear or non-linear, for example. Further, the relations may be a function of various other parameters, such as, for example, transmission gear state, temperature, or others.